1. Field of the Invention
The present invention relates to an image forming apparatus. More particularly, the present invention relates to an image forming apparatus having a structure that restricts the vibration of a rotating shaft, thus improving print quality.
2. Description of the Related Art
In general, image forming apparatuses such as printers and photocopiers for printing images on print papers can be classified according to the method used to form an image. One type of image forming apparatuses is an electrophotographic image forming apparatus. In this type of apparatus, light is scanned onto a photosensitive medium charged to a predetermined electric potential to form an electrostatic latent image on an outer circumferential surface of the photosensitive medium. A developing agent such as toner is provided to the electrostatic latent image to develop the electrostatic latent image into a visible image. The developed image is transferred to a print medium and then fused thereon so that a desired image is printed.
The process of forming an image in an electrophotographic image forming apparatus typically includes a step of transferring an image developed on the photosensitive medium to a print medium. The image forming apparatus may include a transfer belt to transfer the print medium to a transfer position. The transfer belt is supported by a shaft which is rotated by the rotational power of a driving source, such as a motor.
FIG. 1 is a front view illustrating a gear assembly in a conventional image forming apparatus. The gear assembly transfers the rotational power of the drive source to the shaft supporting the transfer belt.
Referring to FIG. 1, the gear assembly includes a shaft gear 16 provided at an end portion of the shaft 20, a drive gear 14 engaged with the shaft gear 16, and a motor gear 12 fixed to the motor shaft 10 of a motor (not shown) that is a drive source and engaged with the drive gear 14. The shaft 20 is installed at a shaft support portion 6 of a frame 5 for the circulation of the transfer belt (not shown). When a door 2 of the image forming apparatus is open, the shaft 20 moved along a guide groove 7 formed in the frame 5 and is separated from the frame 5.
During the image forming process, the motor shaft 10 and the motor gear 12 rotate counterclockwise while the drive gear 14 engaged with the motor gear 12 rotates clockwise. The shaft gear 16 engaged with the drive gear 14 and the shaft 20 rotate counterclockwise.
For easy installation/detachment of the shaft 20, the shaft support portion 6 is slightly larger than the shaft 20. Thus, the shaft support portion 6 supports a lower surface and a side surface of the shaft 20, and a slight gap G is formed between the shaft 20 and an upper surface of the shaft support portion 6. Due to the rotational force of the drive gear 14 and pressure acting on the gear teeth of the gears 14 and 16 which are engaged with each other, a force F acts on the shaft gear 16 and the shaft 20 in a direction along a tangential line between the shaft gear 16 and the drive gear 14. The direction of the force F is gradually inclined upwardly, as shown in the drawing.
The amount of the force F can change according to a change in load of the transfer belt. Due to the change in the amount of the force F, the shaft 20 can shake in the shaft support portion 6. The vibration of the shaft 20 makes the image transfer process unstable, which results in a deterioration in the quality of a printed image.
Accordingly, there is a need for an image forming apparatus with an improved gear assembly which is more stable and produces improved quality images.